This invention relates to a method of diagnosing diseases by noting the streaming potential characteristics of a surface coated with the blood plasma protein of the patient.
The phenomenon of streaming potential is observed when a charged surface is placed in contact with water or an electrolyte solution such as a salt solution. In such a situation, there is a diffuse layer of ions held close to the surface which exactly balances the charge of the charged surface. If the fluid is caused to flow parallel to the charged surface, a charge separation is produced which gives rise to an electric potential difference. This is known as streaming potential.
It is to be noted, however, that there is a diffuse distribution of the attracted ions close to the charged surface, with the result that the electric potential falls off with increasing distance from the surface. When the fluid is caused to move across the surface, resulting in the creation of a streaming potential, the ions comprising the surface layer are stuck to the charged surface and don't move. The first ion movement is just outside this layer at a position known as the shear plane.
The potential of the shear plane may be calculated from the measurement of streaming potential and is known as the zeta potential.
Zeta potential values are determined by mathematical computation from streaming potential values and accordingly are derivative values. They are useful because they are independent of stream flow rates. In the present discussion the two terms "streaming potential" and "zeta potential" are used interchangeably, since they represent two different modes of expression of the characteristic which is useful in the diagnosis of disease by the presently described method.